javascript - How to catch uncaught exception in Promise

Question

Is there any way to globally catch all exceptions including Promise exceptions. Example:

    window.onerror = function myErrorHandler(errorMsg, url, lineNumber) {
        alert("Error occured: " + errorMsg);//or any message
        return false;
    }

    var myClass = function(){

    }


    var pr = new Promise(function(resolve, react){
        var myInstance = new myClass();
        myInstance.undefinedFunction(); // this will throw Exception
        resolve(myInstance);
    });


    pr.then(function(result){
        console.log(result);
    });

    // i know right will be this:
    // pr.then(function(result){
    //     console.log(result);
    // }).catch(function(e){
    //     console.log(e);
    // });

This script will silently die without error. Nothing in firebug.

My question is if I do a mistake and forgot to catch it is there any way to catch it globally?

Answer 1

Update, native promises now do the following in most browsers:

window.addEventListener("unhandledrejection", function(promiseRejectionEvent) { 
    // handle error here, for example log   
});

---

We were just discussing this the other day.

Here is how you'd do this with bluebird:

window.onpossiblyunhandledexception = function(){
    window.onerror.apply(this, arguments); // call
}

window.onerror = function(err){
    console.log(err); // logs all errors
}

With Bluebird it's also possible to use Promise.onPossiblyUnhandledRejection. The calls for done are not needed as the library will detect unhandled rejection itself unlike Q (UPDATE 2016 - I now wrote code for Q and it does this).

As for native promises - they will eventually report to either window.onerror or a new handler but the specification process is not yet done - you can follow it here.